Components of various industrial devices are often subjected to extreme conditions, such as high-temperatures and high-impact contact with hard and/or abrasive surfaces. For example, extreme temperatures and pressures are commonly encountered during drilling for oil extraction or mining purposes. Diamond, with its unsurpassed mechanical properties, can be the most effective material when properly used in a cutting element or abrasion-resistant contact element for use in drilling. Diamond is exceptionally hard, conducts heat away from the point of contact with the abrasive surface, and may provide other benefits in such conditions.
Diamond in a polycrystalline form has added toughness as compared to single-crystal diamond due to the random distribution of the diamond crystals, which avoids the particular planes of cleavage found in single-crystal diamond. Therefore, polycrystalline diamond is frequently the preferred form of diamond in many drilling applications. A drill bit cutting element that utilizes polycrystalline diamond is commonly referred to as a polycrystalline diamond cutter or compact (PDC). Accordingly, a drill bit incorporating PDC may be referred to as a PDC bit.
PDCs can be manufactured in a cubic, belt, or other press by subjecting small grains of diamond and other starting materials to ultrahigh pressure and temperature conditions. One PDC manufacturing process involves forming a polycrystalline diamond table directly onto a substrate, such as a tungsten carbide substrate. The process involves placing a substrate, along with loose diamond grains mixed with a sintering aid, into a container of a press, and subjecting the contents of the press to a high-temperature high-pressure (HTHP) press cycle. The high temperature and pressure cause the small diamond grains to form into an integral polycrystalline diamond table intimately bonded to the substrate, with cobalt in tungsten carbide substrate acting as a catalyst during liquid-phase sintering, to create diamond-diamond bonds from precipitation of carbon from a solid solution of cobalt-carbon. A polycrystalline diamond table thus formed may then be leached to remove the sintering aid from all or part of the polycrystalline diamond. The resulting leached PDC is more thermally stable than similar, non-leached PDC.
Leaching out large portions of the sintering aid results in a thermally stable polycrystalline diamond (TSP) table. At a certain temperature, typically at least 750° C. at normal atmospheric pressure, the TSP will not crack or graphitize, but non-leached PDC will crack or graphitize under similar conditions. TSP may be reattached to a new substrate (the original one on which the polycrystalline diamond was formed often being removed prior to or destroyed in the leaching process) to form a PDC.